1. Field of the Invention
The invention relates to a sensor. Particularly, the invention relates to an image sensor.
2. Description of Related Art
Image sensors fabricated according to a semiconductor fabrication process can be used to sense light projected to a semiconductor substrate, for example, a complementary metal oxide semiconductor (CMOS) image sensor. These image sensors use a sensing unit array to receive light energy and convert the light energy into digital data. However, since absorption depths for a silicon substrate absorbing light of different wavelengths are different, different degrees of cross-talk problems exist between the sensing units. For example, the absorption depth for the silicon substrate absorbing 90% light intensity of a blue light (450 nm) is about 1 μm, and such depth range totally falls within an electric field range of the sensing units. However, absorption depths for the silicon substrate absorbing 90% light intensity of a green light (450 nm) and a red light (650 nm) are respectively 3.7 μm and 8 μm, and carriers generated in the deep of the silicon substrate due to the light are far away from the electric field range of the sensing units, and now a motion pattern of the carriers is diffusion, and the carriers might be absorbed by the adjacent sensing units of other colors. Therefore, the sensing unit of each color cannot only absorb the carriers generated by the light of the corresponding color, so that the color corresponding to a sensing result is incorrect.